New York, Sep 22 (DPA) World leaders committed to reach a significant agreement for curbing climate-damaging greenhouse gas emissions by the end of the year, but promised few specifics during a one-day UN summit on global warming Tuesday.

The US and China, the world's two largest polluters, promised to tackle their emissions and tasked each other with doing more to halt the rise in global temperatures.

UN Secretary General Ban Ki-moon warned that negotiations aimed at reaching a new global climate treaty by a December UN summit in Copenhagen were 'proceeding at a glacial pace'.

Swedish Prime Minister Fredrik Reinfeldt, whose country holds the European Union presidency, said the negotiations were 'close to a deadlock', yet there was no option but to push forward.

Smaller island nations again warned that their livelihood would vanish if the world's major polluters couldn't agree to a deal.

President Barack Obama acknowledged that the US has been slow to respond to the threat of climate change, but said: 'This is a new day.

'We understand the gravity of the climate threat. We are determined to act,' Obama said, noting efforts by his administration to reduce vehicle emissions and promote renewable energy.

But the Obama administration could be hamstrung at the all-important Copenhagen summit, scheduled Dec 7-18, as major legislation to curb US emissions has stalled in the Senate. Obama said it was up to all major polluters to take action.

He called on other countries - especially emerging economies such as China and India - to make the commitments necessary to lower their own growing emissions, in order to reach a new global agreement.

'We cannot meet this challenge unless all the largest emitters of greenhouse gas pollution act together. There is no other way,' Obama said.

Chinese President Hu Jintao said his country was determined to lower its burgeoning levels of greenhouse gas emissions, but tasked richer nations with helping the poor adapt without destroying their economies.

'China has taken and will continue to take determined and practical steps to tackle this challenge,' said Hu, who is the first Chinese leader in 30 years to join the annual opening of the UN General Assembly.

'We should combine our efforts to address climate change with those to promote the growth of developing countries,' he said.